BSF STATUS,RP0 ;强制为一
BSF TRISB,0
BCF STATUS,RP0
MOVF PORTB, W ; 7 usecs later, fetch from DATA_PIN
MOVWF TEMP
BTFSS TEMP, 0
BCF STATUS, C ; its a zero
BTFSC TEMP, 0
BSF STATUS, C ; its a one
RRF I_BYTE, F
MOVLW .4 ; now delay 40 usecs
CALL DELAY_10USEC
DECFSZ INDEX, F
GOTO IN_BYTE_1
MOVF I_BYTE, W ; return the result in W
BSF PORTB,0
RETURN
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